Hi Markus,I'm sorry to hear this. However, we do have a workaround for you which should fix the problem. Please try the following:

Deleting the Trados.Interop.MTTMO2 assembly out of the Windows registry

1. Close all SDL Trados applications. 2. Click on START > Run... 3. Type “regedit” into the dialog box and click on OK 4. Go to the folder HKEY_CLASSES_ROOT\Installer\Assemblies\Global 5. Search in the list on the right hand side for:Trados.Interop.MTTMO2,Version=1.0.0.0,Culture=neutral,PublicKeyToken=4316ebe69d6f1d49" 6. When you found the registry key, highlight it and press delete or right-click on it and choose delete. 7. After you deleted this key manually close the Windows Registry Editor

Deleting the assembly out of the Global Assembly Cache8. Click on START > Run... 9. Type assembly into the dialog box and click on OK 10. The C:\Windows\assembly window opens where you need to search in the list for:Trados.Interop.MTTMO2 11. Right-click on Trados.Interop.MTTMO2 and choose Uninstall 12. A message asking if you really want to delete the assembly appears. Confirm the message by clicking OK 13. Close the C:\Windows\assembly windowRunning SDL MultiTerm registration batch script14. Go to C:\Program Files\Shared Documents\SDL\MultiTerm8 15. Double click on SelfRegister_Verbose.bat 16. Confirm all messages by clicking on OK 17. Try now to start SDL MultiTerm or open a termbase within SDL MultiTerm 2009 / SDL Trados Studio 2009.

I apologise, I understand that the resolution is quite long but we are working on an easier way to solve it.